The LVLConstant for the 1st fusion is 1,1, for the 2nd fusion is
1,33 and for the 3rd fusion is 1,606. The BaseCard is always the
most basic card.

The BoostConstant is 5% if the card isn't maximum level and 10%
if it is.

Card1MasteryBonus is only added if the mastery of Card1 is
maxed.

Things missing: How is mastery bonus calculated? Mastery Bonus
seems to be 37,47% of lvl1 Card. For all fusions using Card+ or
Card++ and so on and so on. I tested this for multiple cards of
different rarity and there are sever…